Suction flow equalizer for mud pumps



3 Sheets-Sheet 1 %m up om. M Q q m Q Q 1 3. mm m I H n In 0 April 26,1960 J. H. WILSON SUCTION 11.0w EQUALIZER FOR MUD PUMPS Filed Nov. 8,1955 April 26, 1960 J. H. WILSON SUCTION FLOW EQUALIZER FOR MUD PUMPSFiled Nov. 8, 1955 3 Sheets-Sheet'2 ill@ a m m 2 S Rm 7 zm A 2/ #0 h m5.6 6 h w xgwwa ew April 26, 1960 Filed Nov. 8, 1955 J. H. WILSON2,934,025

SUCTION FLOW EQUALIZEIR FOR MUD PUMPS 3 Sheets-Sheet 3 INVENTOR. JOHNHART WILSON United States Patent G SEMITIQN FLOW EQUALIZER FGR MUD PUMPSJohn Hart Wilson, Wichita Ffils, Application November 8, 1955, SerialNo. 545,628

8 Claims. (Cl. 103-223) This invention relates to the supplying ofdrilling fluid to oil wells, and is directed more particuarly to adevice for equalizing the suction flow of such fluids to the pump, whichin turn, transfers the fluid to the well.

It is well known in the drilling art, that it is desirable to force adense, viscous fluid, known as drilling mud into the bore of the wellduring the drilling thereof, the mud being pumped from a sump orreservoir and ultimately returned thereto. The function of the mud is tocool and lubricate the rotary drill bit, to remove borings as they areproduced, and to coat or seal the face of the bore. Normally the mudconsists of suspensions of natural clays weighted with such materials asbarytes, hematite, and the like to increase the density, together withvarious natural or artificial gel-forming agents and other adjuncts.

Obviously, the high density and viscosity of such fluids causes them tobe extremely difficult to pump, at least by means of conventionalpiston-type pumps. Thus, with the common duplex, double acting pump, anda fluid weighing ten or more pounds per gallon, the maximum pumpingspeed that can be attained, is about sixty strokes per minute. if thisspeed is exceeded, cavitation results, which is to say, that the face ofthe piston on the suction stroke pulls away from the mud in thecylinder, creating a void between the mud and the piston face, so that,on the return stroke, the piston rams into the mud, subjecting thepiston and its driving mechanism to tremendous impact or shock, which,if repeated a sufiicient number of times, will actually pound the pumpto pieces. it is the opinion of the inventor that if it were possible tomove the fluid from sump to pump at a uniform rate of flow, the speed ofthe pump, and accordingly, its capacity could be greatly increased,possibly as much as 50% to 60%.

Many devices to achieve this result have been made such as floodedsuctions; or pressure charging has been used, and they do permit anincrease in speed, but flooded suctions are not always possible, andpressure charging has many disadvantages.

It is therefore an object of this invention to provide a device adaptedto be interposed in the suction conduit of a mud pump or the like,between the sump and pump, which will tend to equalize the flow of thefluid in the conduit.

More particularly, it is an object of the invention to provide a suctionflow equalizing device for piston pumps comprising a housing, movablemeans associated with said housing to form a variable volume charnber incommunication with the suction line of a pump. Spring means for actingupon said movable means to urge the latter in one direction, thevariable fluid pressure acting on said movable means to urge saidmovable means in the other direction. Variable pressure means connectedto said chamber for maintaining fluid pressure thereon to adapt a pumpsuction system to various conditions of operation.

A further object of the invention is the provision, in

a device of the character described, of indicating means to facilitatethe initial setting of the device, i.e. its adjustment to the particularpump with which it is to be used, and for observing the operation of thedevice from time to time.

Other objects and advantages will be revealed by the following detaileddescription, when read in conjunction with the accompanying drawings, niwhich like reference characters designate like parts in the severalviews thereof, and in which:

Fig. l is a fragmentary side elevational view of a mud pump, with partsbroken away and shortened, and showing a suction line leading to the mudpump, with a suction flow equalizer interposed within the mud pumpsuction line, and showing the relationship of the suction flow equalizerto the mud pump,

Fig. 2 is an enlarged vertical sectional view through the suction flowequalizer and through a portion of the suction line leading to the pump;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2, looking inthe direction indicated by the arrows;

Fig. 4 is a sectional view taken on the line 4-4 of ig. 2, looking inthe direction indicated by the arrows;

Fig. 5 is an enlarged fragmentary sectional elevational view of theequalizer cylinder showing the diaphragm in its uppermost position; Fig.5A shows diaphragm of Fig. 5 in its lowermost position;

Fig. 6 is a reproduction of an actual synchronized pressure graph, astraced on a card by a steam indicator graph instrument, before theinstallation of the suction flow equalizer in the suction flow line,with the pump working fifty-four strokes per minute;

Fig. 7 is a view similar to Fig. 6, but of a card graph made on the samepump operating under the same conditions, but after the installation ofthe flow equalizer on.

the suction line of the pump;

Fig. 8 is a view similar to Fig. 7, but the graph is taken from a pumpusing aslightly smaller diametercylinder, and with the speed of the pumpbeing increased the pump as possible, a device which functions as anac-.

cumulator, to receive a portion or charge of the mud during one part ofthe pumping cycle, and to release that portion during another part ofthe pumping cycle.

This device comprises a cylinder, which cylinder opens into the suctionconduit of the pump, a piston in the cylinder, a diaphragm seal betweenthe piston and the cylinder, and a compression spring acting on thepiston in a direction to draw mud fluid into the receiving chamber 11;and air pressure in the upper chamber 27 pushing downward on thediaphragm 62 and piston 44. The upper chamber 27 is sealed at the topand is connected to an air supply 92 through a regulator to maintain aconstant reduced air pressure, in this chamber.

Turning now to a detailed description of the invention, in the drawings,the letter S designates a sump or reservoir containing a suitable supplyof drilling fluid or mud. A suction conduit C extends from the sump S tothe pump P, the discharge port D of which is connected to a suitablepipe (not shown), which extends to the bore hole of the well (notshown). The pump is preferably of the reciprocating, duplex, doubleacting type, and is well known in the art of drilling. The two crankunits do not operate degrees out-of-phase, but approximately ninetydegrees out-of-phase, so that one unit is just beginning a stroke whenthe other unit is at about Patented Apr. 26, 1961} 'will be more fullyexplained hereinafter.

asagoae the mid-point of its stroke. Consequently, at least one of theunits is actively pumping at all times, and the rate of flow tends to bemuch more uniform than would be designated generally by the letter B. Toform the equalizer, a pipe T 1 issituated within the suction conduit C,with the lateral opening 2 thereof being connected to receivingrchamber11 which is formed by cylinder it with the cylinder preferablyextendingvertically, arms'of the T being connected to the suction sideof the pump P and to the conduit C leading to the sump S, respectively,by means of the respective threaded union couplings 4, with sealinggaskets 6 (Fig. 2) interposed betweenthe respective adjacent faces ofthe T and con duits. The remote end of the outlet 2 is provided withan'outwardly extending flange 8 on which cylinder 16 is secured, as byWelding as indicated at 12. The upper end of cylinder 10 has atiiange 14thereon, which flange has an annular groove 16 formed therein, as isbest brought out in Figs. 5 and 5A. The flange 14 nas the inner corner13 thereof rounded, as will be more fully explained hereinafter.

A flange 20 has an annular groove 22 formed therein, which annulargroove is complementary to the annular groove 16 of the flange 14. Theflange 20 is superposed on the flange 14 so that holes formed in therespective flanges will receive bolts24. A'short length of cylindricaltubing 26 is secured to flange 20, so that the tubing 26 will be inaxially aligned relation with the cylinder 10. The flange 29 hasa'rounded corner 23 thereon, as The upper end of the cylindrical tubing26 is closed by a plate 39 of larger diameter than that of tubing 26,providing an outturncd flange, which flange has circumferentially spacedholes therein to receive bolts 32 which extend therethrough and throughthe out-turned flange portion of-plate'34, which is secured to the lowerend of cylindrical spring housing 36. H

The respective plates 30. and 34 have holes therein, which holes areaxially aligned withthe cylinders 16 and 26, so as to permit the pistonrod 38 to pass therethrough. The cylindrical spring housing 36 is closedat its remote end by a cap'40 which is held in place by detachableconnecting bolts 42.

The term housing as employed in the appended claims is intended toinclude the structure jointly exemplified by the elements 16, 26, 36 and4t).

rod 38. The circular plate 48 is slightly smaller in (ii-- ameter thanthe diameter of the cylindrical opening in the cylindrical springhousing 36, so the plate will perform the dual function of guiding theupper end of the piston rod, and will serve as a retainer for one end ofa compression spring 52 which functions as a resilient means urging thediaphragm 62 and piston 44 in a direction opposite to the direetionrinwhich these parts are urged byfthe gas or air pressurehereinafterdescribed in more detail. The other end of the compressionspring 52 rests upon the upper face of plate 30.

a custion for the piston head in its extreme upward position. Holes 59which are formed through plates 30 and 34, form connecting passagesbetween chambers27 and 37;

An annular ring 60 is positioned witmn cylinder in on flange 8 so as toserve as a cushion member for piston 44, when said piston is .in thelowermost position. In this manner the piston 44 is cushioned at each 7end of the cylinder, so as to absorb shock, thereby preventing thepiston from coming to an abrupt stop.

A diaphragm 62 is employed to enhance the effectiveness of the piston44-and'to form a positive seal between the piston .44 and the cylinder 10,with a minimum of friction loss. The diaphragm is substantially annularin form, and is preferably constructed of a combination of a fabric andan elastomer, with the inn'erand outer edges 64 anddti of the diaphragm62 taking the form of large O-shaped beads, as will best be seen inFigs. 5 and 5A. The inner Q-shaped bead edge tits in complementarygrooves formed in the element comprising the upper faceof the cup-shapedpiston 44 and in the lower face of a plate 68, as'wili best be seen inFigs. 5 and 5A, while the outer O-shaped bead fits in the previouslydescribed complementary grooves '16 and 22. The piston 44 is spacedinward from the cylinder it co es to form an annular space therebetween,which spacelrnay be from one-half to three-quarters of an inch in width,so that the diaphragm may work freely without sharp bending, which wouldresult in damage to the diaphragm 62 which spans the annular spacebetween the cylinder 10 and the piston 44. In this manner the piston 4may work through a relatively long stroke with a minimum of fatigue tothe diaphragm 62, which will prolong the life of the diaphragmmaterially. The particular type of diaphragm used is of a characterwhich does not stretch materially, but performs a positive sealingaction between the piston 44 and the cylinder 1:), and'obtains thenecessary movement by a bellows or rolling action of the diaphragm 62during the movement or" the "piston 44. The circumferential edges oftheupperportion of piston 44 and plate 68, which are in contact with-thediaphragm 62, have rounded corners 7t) and 72, respectively, as do theinner edges of flanges 14 and 20, respectively, thereby relieving thediaphragm 62 of a substantial amount of fatigue at these points.

A nut 74 bears against a plate '76, which plate is welded to piston 44so as to hold the piston securely against longitudinal movement withrespect to piston rod 38.

The upperend of piston rod '33 is threaded to receive 7 acorrespondingly threaded pointer 78, which may be by means of a lock nut80. The cylindrical spring'housing 36 has a transparent sight Window $2011 each side thereof in transverse aligned relation and preferablyoffset with respect to the'center. Each sight window 82 has a transversehorizontal mark thereon to enable the correct aligning of the adjustablepointer 78 with the mark, when the piston rod 38 is correctlypositioned, that is, with the piston 44 at the mid-point of the travelof cylinders 10-26, which is the preferred setting for'the pointer 78 toalign with transverse mark 83, to give the maximum working movement ofpiston 44in each direction. 'It is preferably to have the sight windows82-fitted between gaskets so that air pressure may be maint ed Withinthe cylindrical spring housing 36.

Thc'compression spring 52 is a spring of a strength.

to'give the correct calibrated suction equalization, as will A gasket 84is provided intermediate the upper end of the cylindrical spring housing36 and the lower end of cap 40 so as to form a seal therebetween. Thecap 40 has a bail 86 thereon for convenience in handling the device witha hoistline or the like.

An inlet opening 88 is provided in a side of housing 36 for introductionof air under pressure, through an adjustable pressurerregulator 90, fromaline 92 used in supplying air to the housing for impressing a positivepressure on diaphragm 62, as will be more fully explained hereinafter.

A threaded connection 94 connects housing 36 with a pressure gauge 96,which enables the determining of the pressure within the housing 36. Anadjustment screw 98 is provided to adjust the pressure within housing 36to the desired degree, irrespective of the pressure in the line 92.

Operation In the pumping of drilling fluid with a two cylinder,double-acting pump, which pump is usually known as a duplex pump, fourfluid pressure impulses and four fluid suction impulses are had on eachrevolution of the crankshaft of the pump, and since the intake of thesuction line or conduit C is a substantial distance from the intakevalve of the pump P, and with the viscosity of the drilling fluid beingconsiderably in excess of that of water, a lag in the movement of thedrilling fluid is present. However, once this heavy fluid starts movingit possesses considerable inertia.

In the operation of a conventional pump during part of the cycle, twopistons are sucking mud, and this amount of suction accelerates the flowof mud in the suction conduit C to a velocity sufficient to take care ofthe demand of the two pistons. As may be seen from Fig. 6, this requiresup to eight pounds suction pressure or vacuum to accelerate this flow.The mud hardly reaches this velocity until one of the cranks reachesdead center and that piston stops sucking mud. When this occurs, the mudflowing in conduit C is of a greater aroount than is required for thesuction of one piston, therefore, something must decelerate the flow ofmud in conduit C to the amount required by the suction of one piston.The only thing that can decelerate this flow is positive pressure, andthis positive pressure actually builds up in conduit C, upon the closingof an iniet valve, as shown by the indicator card, Fig. 6, and in oneinstance, as shown by this card, the pressure built up to twenty threepounds above atmospheric pressure. This repeats four times eachrevolution of the pump. If the pump runs too fast the fiuid will fail tofollow the piston on the suction stroke, and on the return stroke, thepiston will meet the fluid coming into the cylinder at considerablevelocity. This will cause a pounding action, which, if continued, willactually destroy the pump, or some parts thereof.

For the purpose of illustrating the method of operation of the pump, itmay be assumed that the flow qualizer E is installed the suction line ofa pump, and that the spring 52 is a 100 lb. spring, that is, a springsuch that an additional 100 lbs. of pressure is required to compress thespring each additional inch within the elastic limits thereof, and thatthe spring 52 is adjusted so that, with the piston at the top of thestroke, the spring will have a pressure of 600 lbs. and at the bottom ofthe 6 stroke, a pressure of 1200 lbs. If an air pressure of about 8 lbs.above atmospheric is exerted upon the diaphragm 62 on the upper side,and 3 lbs. suction or negative pressure acts on the lower side of thediaphragm, a total of ll lbs. p.s.i. acts upon the diaphragm 52, towhich the piston rod 38 is connected through piston 44. If the effectivepiston area is approximately 90 square inches, the total pressure actingon the piston is approximately 100 lbs, under which condition the pistonwould stop approximately 2" from the bottom of travel at the point wherethe spring would have a compressive tension of 19% lbs.

With 8 ibs. pressure above the diaphragm and 1 lb. vacuum pressurebelow, or a total of 9 lbs, pressure on 90 square inches which would beabout 800 lbs. total pressure, the piston 4-4 would come to rest at apoint two inches below the top of the possible stroke or four inchesfrom the bottom of the possible stroke. Operating under theseconditions, the piston 44 would float within cylinder 10 between twoinches from the bottom and two inches from the top position, in otherwords, would have a movement of 1" above and 1" below the midpoint ofthe cylinder 10. Thus the piston displacement is approximately 180 cubicinches, and calculation indicates that a displacement of this amount isrequired to equalize the flow of the fluid in the suction conduit C tocompensate for the variable demand of the four suction chambers of aduplex pump of conventional 7 /2" 7; 14", size.

The conditions as set out above, present an ideal operating condition,and in view of this, air pressure is introduced through pipe 92, andregulator is set to maintain 8 lbs. pressure within the spring housing36, which is sealed and is in communication, by means of vent holes 55,with a chamber in cylinder 26 above diaphragm 62. By maintaining thepressure and with the spring balanced in this relation, the pump may berun seventy five or more strokes per minute without a positive pressurebeing created within the suction line, and the pump will run smoothlyand the cylinders will load perfectly. But no pump can be run fasterthan that speed where the fluid fails to follow the piston on thesuction stroke, for if this speed is exceeded, the pump will pound andultimately destroy itself.

As pointed out, the chart shown in Fig. 6, was graphed by a pressureindicator attached to connection on the suction side of the pump, whichshows the pressures and suctions present in the suction lines C and C,through approximately four revolutions of the crank shaft of the pump.It is to be noted that a positive pressure, as high as twenty threepounds per square inch, existed in the suction line for a period duringone revolution of the crankshaft, and that suction pressures of 8 psi.below atmospheric pressure occurred on many strokes.

Since the spring 52 must be selected to meet the requirements of thepump with which it is to be used, no set figure can be given for thetension of the spring. However, for purposes of illustration, thefollowing discussion will be based upon a 7.5" diameter by a 14" strokemud pump, running fifty-four strokes per minute, with or without theflow equalizer, and also upon the same pump with a 7" liner, running 75strokes per minute.

Pig. 7 shows an actual indicator card taken at slightly more than onerevolution of the pump, with the pump running fifty four strokes perminute, with 7 /2 liners, sucking from a pit four feet below the levelof the pump and pumping with nine pound mud through an 8" suction morethan thirty feet long, and with the pump running smoothly and withoutpounding. It is obvious, from this card, that the pump could be run muchfaster, therefore the pulley size was changed and the pump speeded up to75 strokes per minute, and an indicator card, as shown in Fig. 8, wastaken. The operating conditions were otherwise the same as those underwhich the card in Fig. 7 was made, except the liner size was reduced toseven inches to avoid pumping too much mud. As can be seen from thecard, Fig. 8, the suction pressure was at all times, below atmospheric,and varied from about one pound below to about three pounds belowatmospheric pressure- The pump ran quietly and the cylinders loadedperfectly.

With the proper pressure on the diaphragm 62 and the proper springpressure on piston rod 38, the surge of mud will move the piston upwardto fill or to partially fill cylinder 1% below the diaphragm 62,whereupon, upon the suction being increased, the mud will flow uniformlythrough the valves into the pump cylinders, thereby maintaining the flowthrough the pump at a substantially uniform pressure, hence volume, asindicated in the graphs of Figs. 7 and 8.

The operating conditions of the equalizer may be visually observed bynoting the movements of the annular pointer- 78, which should have amean position register with the transverse mark 83 on transparent win:dow 82. Should the mean position of the pointer change, the pressureindicated by gauge 96 can be immediately'hoted and the proper pressurerestored to housing 36 by manipulation of screw 98 of regulator 90, soas to maintain the mean positionof the pointer 78 in proper relationwith the transverse mark 83.' ,By so doing, the piston 44 is broughtback to the midpoint operating position Within the cylinder 10. .Havingthus described the invention, what is claimed 'is' i.

1. In combination with a piston pump of the reciprocating type and a'suction line communicating with said pump,'a suction fiow equalizercomprising a cylindrical accumulator, a piston reciprocable axially insaid ac cumulator, sealing means between said piston and saidaccumulator, said, piston and said sealing means forming two variablesized chambers within said housing,

means for placing one of said chambers in communica:

tion with said suction line, resilient means operatively V comected tosaid piston exerting relatively opposing axial forces substantialhgreater than the effect of at-' mospheric pressure against said pistonand normally urging said piston to an axial position of balanceintermediate of its stroke in the accumulator, said suction linecommunicating with the accumulator on one side of said piston, wherebythe creation of high pressures in the suction line will store pumpedfluids in said accumulater and displace the piston against the force ofone said means, and responsive to a subsequent reduction in pressuresaidlastmentioned means will urge the piston in a direction to expel fluidfrom said accumulator.

to said housing, a piston connected to said diaphragm I and therewithforming two variable size chambers within the housing, means for placingone of said chambers in communication with the suction line of the pump,a

' pistonrod-within the other chamber afiixed to and ex tending from saidpiston, means communicating with said otherchamber for maintaining a gasabove atmosgara es pheric pressure within .said other chamber tourge-said diaphragm in one direction, and a spring .of a strengthapproximately equalling the thrust of said gas pressure acting uponsaidpistonrod to urge said diaphragm in the otheridirection and toward aposition ofbalance intermediate of the stroke of said diaphragm.

5. The device defined in claim 4, in cluding means to regulate said gaspressure in saidotherchamber.

6. In combination with a piston pump, and a suction line communicatingwith the intake side of said pump, a StiLliOllfiOW equalizer comprisinga fluid tight housing, a diaphragm within said housing and attachedthereto and forming therewith chambers of variable volume on oppositesides of said diaphragm, means for placing one of said chambers incommunication with said suction line, means for maintaining a gaspressure above atmospheric against said diaphragm in the other of saidchamhers to urge the diaphragm in one direction, and resilient means ofa-strength approximately equalling the thrust of said gas ,pressurefor.urgingsaid diaphragm in the other direction and toward a positionofbalance intermediate of the stroke of said diaphragm. I

7; The device defined in claim 6, including means to regulate said gaspressure and means to adjust the pressure exerted by said resilientmeans operatively associated with said means for maintaining gaspressure.

8. The device defined in claim 6, including means connected to saiddiaphragm and to indicate visibly the position within said housing ofsaid movable means, and transparent means within the wall of saidhousing to permit such visibility.

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